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Old Growth Forests and Climate Change Talking Points

Old Growth Forests and Climate Change Talking Points

What is an Old Growth Forest?

According to the Food and Agriculture Organization of the United Nations, old-growth (or primary) forests are naturally regenerated forests of native tree species where there are no clearly visible indications of human activity, and the ecological processes are not significantly disturbed.

Old-growth features include diverse tree-related structures that provide diverse wildlife habitat, increasing the biodiversity of the forested ecosystem. These structures include:

  • Multi-layered canopies and canopy gaps.
  • Greatly varying tree heights and diameters.
  • Diverse tree species and classes and sizes of woody debris.

What is a Mature Forest?

Mature forests contain trees generally around 80 years of age—although that can vary widely depending on geographic location, tree species, and other factors. Most mature forests are second-generation forests resulting from logging, but some are the consequence of fire, wind, disease, or other causes.

For the purpose of protecting these climate-critical forests from logging, the baseline definition for a mature forest should be 80 years. By establishing the age of mature forests and trees at 80 years, federal agencies will establish a safety net that assures minimum protection of the ecological and carbon benefits they provide for future generations. These forests collectively contain the bulk of the carbon already stored in federal forests and they continue to sequester carbon at high rates. They also provide, across forest types, vital habitat and biodiversity benefits, and important sources of drinking water for communities.

Critically, protecting mature forests and trees today will provide the foundation to recover old growth ecosystems which have largely been lost to logging across the landscape

Confronting the Climate Crisis — The Missing Piece of U.S. Climate Policy

  • Reducing emissions alone is an insufficient strategy for addressing the climate crisis we face today — the U.S. must also pull and sequester legacy emissions from the atmosphere. 
  • While there are numerous promising technologies that can help us meet this need in the future, our best near-term opportunities are natural climate solutions that enable us to store vast amounts of carbon in our forests. Conserving mature and old growth forests offers the most significant, straightforward ways to leverage this potential. 
  • To fully address the threat of climate change, we must transform our economy, fully decarbonize the electricity sector, and electrify the transportation sector. In comparison, protecting and recovering old growth forests is a simple, cost-effective climate solution that should have been realized decades ago. 
  • A climate forest policy is the “missing piece” of U.S. efforts to address the climate crisis. 
  • Of the human-caused global CO2 emissions since 1870, 26 percent is due to emissions from deforestation and forest degradation (Le Quéré et al. 2016).
  • Older, mature forests have the greatest potential to sequester and store significant amounts of carbon, and to recover carbon that has been released to the atmosphere over the last 200 years (Oregon Global Warming Commission 2018). 

Why Mature and Old Growth? 

  • Experts estimate that as much as 95% of primary forests (those that have never been logged) have been lost in the United States. We must protect what’s left, and strive to recover what’s been lost. 
  • Protecting the mature trees and forests of our federal forestlands is our best chance for recovering old-growth that’s been lost. 
  • There is a pressing need for federal natural resource agencies to also evolve into carbon management agencies, starting with the management of forests on federal lands. 
  • Older trees and forests are the keys to the shift.  They sequester carbon at high rates and store it for long periods of time.  And even when an older tree dies, it can retain most of its carbon for decades–if not centuries–if left in the forest. Safeguarding this carbon i is critical to protecting communities from the future impacts of climate change.

Essential Support for Community Protection

  • Mature and old growth forest watersheds protect both drinking water quality and quantity (Segura et al. 2020, Perry et al. 2016). 
  • Bigger, older trees tend to be naturally more resistant to fire–they have thicker protective bark on bigger, older trees, possess higher multilayer canopies that keep temperatures cool, and enable the forest to retain more moisture in the air and soil. (Lesmeister et al. 2019, Zald et al. 2018). 

Fighting Biodiversity Loss 

  • Wildlife corridors and climate refugia (areas that maintain natural microclimates) help wildlife move and find suitable habitat in a rapidly changing world. Many of these features can be enhanced or restored by protecting mature and old growth forests. (Watson et al. 2016).

Regional Talking Points 

Pacific Northwest 

  • Temperate moist forest types can have higher biomass carbon density than both boreal and tropical forests (Keith et al 2009). 
  • Moist, temperate forests in the western United States that have medium to high potential carbon sequestration and low future climate vulnerability could account for approximately 8 years of regional fossil fuel emissions (Buotte et al. 2019).
  • In the Pacific Northwest forests, harvest was the dominant cause of tree mortality (2003–2012) and accounted for fivefold as much mortality as that from fire and beetles combined (Berner et al. 2017).
  • One study found that 65 percent of the carbon from Oregon forests logged over the past 115 years remains in the atmosphere, and just 19 percent is stored in long-lived products. The remainder is in landfills (Hudiburg et al. 2019)


  • Less than 1/10 of 1% of Vermont forests resemble the natural, old-growth ecosystems that once dominated the region (Zaino et al 2018). 
  • Just 3% of New England forests are managed to restore the region’s natural, old-growth forests (Moomaw et al 2019).
  • New England forests could store 2-4X the amount of carbon as current levels if allowed to grow older (Keeton et al 2011).
  • 30% of the aboveground forest carbon in the Northeast US is located within protected areas that cover just 5% of the land area (Congressional and State Wilderness areas and similar) (Lu et al 2013).